Plasmon surface polaritons (PSPs) are bound non-radiative electromagnetic waves that arise due to polarization charges which travel along a metal/dielectric interface (cf. E. Burstein, W. P. Chen, Y. J. Chen and A. Hartstein, J. Vac. Sci. Technol. 11 (1974), 1004). Their field intensity is at a maximum at the metal surface and decays exponentially perpendicular to the interface not only into the metal but also into the dielectric (cf. H. Raether, in: Physics of Thin Films (eds. G. Hass, M. H. Francombe and R. W. Hoffmann), vol. 9, 145-261, J. Wiley, New York 1977).
As a consequence of dissipative and radiative losses these waves are also damped in their propagation direction (cf. T. Inagaki, K. Kagani and E. T. Arakawa, Phys. Rev. 824 (1981), 3644, and B. Rothenhausler, J. Rabe, P. Korpiun and W. Knoll, Surf. Sci. 137 (1984), 373). The interest in PSPs has increased in recent years since they have been successfully used for field enhancement in various surface spectroscopic studies on adsorbates and thin films (cf. Electromagnetic Surface Excitation, R. F. Wallis and G. I. Stegeman, eds., Springer, Berlin 1986).
PSPs can be considered a surface-specific light (cf. W. Knoll, B. Rothenhausler and W. Hickel, SPIE Proceedings, Los Angeles, 1989) whose optical phenomena are similar to those for plane electromagnetic waves. Examples are diffraction of PSPs by a dielectric phase grating (cf. B. Rothenhausler and W. Knoll, Appl. Phys. Letters 51 (1987), 783), interferometry between PSPs and a driver photon field (cf. B. Rothenhausler and W. Knoll, J. Opt. Soc. Am. 85 (1988), 1401), and surface plasmon microscopy (cf. B. Rothenhausler and W. Knoll, Nature 332 (1988), 615).